The present invention relates to heat conducting polymer mold products, which conduct heat generated by electronic appliances, etc. In particular, the present invention relates to heat conducting polymer mold products that can realize a superior heat conducting property.
Recently high density packaging of semiconductor packages and high integration and high speed of LSI that are stored inside the electronic appliances are required in accordance with high performance, reduced size, and lightweight of electronic appliances. Measures for efficiently dissipating heat from the electronic components to the outside became very important because heat generated in various electronic components is increasing with the above described trends. As a heat dissipating member, heat conducting mold products comprising heat dissipating materials such as metal, ceramics, polymer compositions etc., are used for printed-wiring assemblies, semiconductor packages, casings, heat pipes, heat dissipating plates, and heat diffusion plates, etc.
Among the above heat dissipating members, heat conducting mold products comprising polymer compositions (hereinafter referred to as “heat conducting polymer mold products”) are widely used because they are easily molded in any shapes and they are relatively light in weight.
Known polymer compositions for forming heat conducting polymer molds include compositions in which one or more heat conducting filler(s) with high heat conductivity are blended in matrix polymer material comprising for example resin or rubber. Metal oxides such as aluminum oxide, magnesium oxide, zinc oxide, quartz, etc.; metal nitrides such as boron nitride, aluminum nitride, etc.; metal carbides such as silicon carbide: metal hydroxides such as aluminum hydroxide; metals such as gold, silver, copper, etc.; carbon fibers; and graphite are used as the heat conducting fillers.
On the other hand, polymer compositions containing thermotropic liquid crystal polymer are used as matrix resin in the applications where deformation of the mold products due to high temperatures should not occur during packaging process or during its use. A thermotropic liquid crystal polymer has good workability and has superior heat resistance. An electric insulative composition having good heat conductivity, which comprises 50-90 wt. % zircon and 50-10 wt. % thermotropic liquid crystal polymer, is disclosed in Japanese Laid-Open Patent Publication 5-271465. Further, a composition comprising 20-80 wt. % heat conductive filler such as carbon fiber and 80-20 wt. % thermotropic liquid crystal polymer is disclosed in Japanese PCT National Phase Publication 2001-523892.
The physical properties of the liquid crystal polymer depend on three dimensional structure and orientation degree of the molecular chains included in the liquid crystal. The polymer chains are arranged in a crystal structure specific to each of the polymers partly in the liquid crystal. As a method to observe the arrangement of the polymer chains, X-ray diffraction is used.
However, heat conductivity is insufficient in the heat conducting polymer mold products obtained by the above described conventional art because amount of heat released from the electronic components is increasing due to its high performance.
The present invention is provided in view of the problems that were inherent in the conventional art. An object of the invention is to provide heat conducting polymer mold products that realize superior heat conductivity.